(7S,9S)-9-Acetyl-9-amino-7-[(2-deoxy-β-D-erythro-pentopyranosyl)-oxy]-7,8,9,10-tetrahydro-6,11-dihydroxy-5,12-naphthacenedione (hereinafter, referred to as amrubicin) of the following formula (1):
and a salt thereof have been known to be useful as a chemotherapeutic agent for cancers (see, for example, JP-B-3-5397, the corresponding U.S. Pat. No. 4,673,668). The hydrochloride of such amrubicin may have several kinds of crystal forms, and it has been known that among them, specific crystals thereof are excellently stable to heat (see, for example, Japan Patent Gazette No. 2975018, the corresponding U.S. Pat. No. 4,952,566).
Anthracycline compounds such as amrubicin are unstable in a solution state, and when formulating such a compound as an injection, it is usually formulated in the form of a powder or a lyophilized product which is dissolved when used.
As a preparation of stabilized amrubicin, a preparation incorporated with L-cysteine or a salt thereof has been known (e.g., Japan Patent Gazette No. 2,603,480, the corresponding U.S. Pat. No. 6,376,469).